High-temperature rupture failure of high-burnup LWR-MOX fuel under a reactivity-initiated accident condition

• Published in: Annals of nuclear energy 2024-01, Vol.195, p.110144, Article 110144
• Main Authors: Taniguchi, Yoshinori, Mihara, Takeshi, Kakiuchi, Kazuo, Udagawa, Yutaka
• Format: Article
• Language: English
• Subjects: Fuel failure; Fuel performance codes; High-temperature rupture; LWR fuel; M5™ cladding; MOX fuel; Reactivity-initiated accident
• ISSN: 0306-4549
• DOI: 10.1016/j.anucene.2023.110144

•A reactivity-initiated accident (RIA)-simulated test on 64 GWd/t high-burnup mixed-oxide (MOX) fuel rod sheathed with M5™ cladding resulted in fuel failure.•The failure is interpreted as a high temperature rupture, driven by rod internal pressure increase associated with transient fission gas release.•The proposed mechanical state parameter dedicated to predicting plastic instability is easy to implement in fuel performance codes and works as an effective index for evaluating the risk of rupture failure during RIAs. A reactivity-initiated accident (RIA)-simulated test CN-1 on a high-burnup 64 GWd/t mixed-oxide fuel rod sheathed with M5™ cladding was conducted at the Nuclear Safety Research Reactor, resulting in fuel failure. A small opening with slight ballooning deformation characterized the post-test visual appearance of the test fuel rod. Simulation using fuel performance codes FEMAXI-8/RANNS predicted rod survival under early phase loading induced by pellet-cladding mechanical interaction and subsequent boiling transition, and the cladding-surface temperature measured online confirmed the occurrence of boiling transition. The experimental observation and simulation indicate that the failure was caused by a high-temperature rupture following increased rod-internal pressure. The RANNS sensitivity analysis revealed that a mechanical state parameter dedicated to predicting plastic instability might be an effective index for evaluating the risk of rupture failure during RIAs.